Since the immune system is impaired in the course of HIV-infection, the purpose of any AIDS vaccine therapy should be the restoration in the patient of an adequate immunocompetence to enable him to respond to the antigenic stimulus represented by the virus. In the present investigation we have shown the antiproliferative action on activated T-cells in culture of: sera taken from HIV-infected, but not seronegative individuals; T lymphocytes taken from seronegative subjects and infected in vitro with HIV but not non infected cells; native alpha-IFN and the time-dependent inactivation of this activity by formaldehyde treatment of alpha-IFN. Thus is confirmed the major contribution provided by alpha-IFN to the immunosuppression occurring in the course of HIV-infection. These results also strongly support the new AIDS vaccine therapy strategy based on the administration to HIV-infected patients of inactivated, but still immunogenic alpha-IFN. To the alpha-IFN treatment could also be combined the administration of fixed autologous suppressive cells. The induction of gamma-IFN in addition to alpha-IFN production by stimulation of cells from healthy donors with gp120 should encourage the use of a vaccine combining both inactivated alpha-IFN and gamma-IFN. On the other hand, the IL-12 cytokine with its potential to restore compromised cell-mediated functions associated with HIV infection should also be a valuable adjuvant treatment.